For example, in continuous casting for steel, molten steel poured into a mold is cooled by a cooling means, whereby solidified shell grows and a casting product is drawn from below the mold. Here, the casting product drawn from the mold has not completely solidified at the point in time when coming out of the mold but has an unsolidified portion therein. Therefore, there is a possibility that so-called bulging deformation of the casting product being deformed to bulge out occurs due to static pressure of the molten steel in the mold. It is known that center segregation occurs at a region where the bulging deformation occurs.
To suppress the bulging deformation, continuous casting facilities provided with casting product support rolls that come into contact with long side surfaces of the casting product drawn from the mold and receive the aforementioned static pressure are suggested, for example, in Patent Documents 1, 2.
Here, to surely support the long side surfaces of the casting product, it is effective to decrease the roll diameter and decrease the interval between the casting product support rolls. However, if the roll diameter is decreased, the casting product support roll becomes insufficient in stiffness and deformed to deflect due to the static pressure, thus failing to surely support the casting product.
Hence, in Patent Documents 1, 2, backup rolls that support the casting product support rolls are arranged to prevent the aforementioned casting product support rolls from being deformed due to the static pressure.
Further, porosity may occur inside the casting product due to solidification contraction or the like. The porosity can be decreased by applying strong rolling reduction to the casting product during hot rolling, but the rolling reduction amount during the hot rolling cannot be secured to fail to sufficiently decrease the porosity in the case of a product with a large thickness.
Hence, to suppress the occurrence of porosity at the stage of the casting product, a roll segment apparatus that applies rolling reduction to the casting product is suggested, for example, in Patent Document 3. In this roll segment apparatus, a reduction means that brings a lower frame and an upper frame closer to each other and thereby can apply reduction to the casting product.
Here, in the roll segment apparatus described in Patent Document 3, a roll in contact with the casting product is composed of divided rolls divided in a roll axial direction, and bearing parts that pivotally support the divided rolls are arranged between divided rolls adjacent in the axial direction. This structure makes it possible to receive a load applied on the roll by a plurality of bearing parts in a distributed manner, and to apply reduction to the casting product with a large rolling reduction force to decrease the porosity.